Johannsenite

inosilicate

metamorphic

Formula: CaMnSi2O6
Inosilicate, pyroxene
Specific gravity: 3.56
Hardness: 6
Streak: White
Colour: Blue-green, grey-white, dark brown, colourless
Environments:

Metamorphic environments

Johannsenite is found in contact metamorphic environments

Alteration

johannsenite and H2O to rhodonite and xonotlite
6CaMnSi2O6 + H2O → 6Mn2+SiO3 + Ca6Si6O17(OH)2
At Pueblo, Mexico, johannsenite occurs in calcite veins in rhyolite and is altered to rhodonite and xonotlite according to the above equation (DHZ 2A p421).

Common impurities: Ti,Al,Fe,Mg,Na,K,C,P,H2O

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